The Hindustani music ragam Sahana is an upper-tetrachord-dominant Kanada-anga raga, from the Kafi thaat, also allied with Bageshree and Bhimpalasi.
Its ārohaṇa-avarohaṇa structure (ascending and descending scale) is as follows (see swaras in Carnatic music for details on below notation and terms): The notes used in this scale are Shadjam, Chathusruthi Rishabham, Antara Gandharam, Suddha Madhyamam, Panchamam, Chathusruthi Dhaivatham and Kaisiki Nishadham.
Sahana has a distinct mood due to these phrases and characteristic gamakams and is rarely confused with other ragams.
It was evolved in the public domain, enjoyed the airtime with listeners and musicians and then it became important enough to be inducted into the portals of our music as a formal raga, distinct in its svarupa, appeal and capable of being moulded into compositions.
[1] The jeeva swaras : R₂ - rishabham, G₂ - gandharam and N₂ - nishadam provide extraordinary ranjana.